Sectionalized traveling wave tube assembly



June 13, 1967 H. L. LEVIN SECTIONALIZED TRAVELING WAVE TUBE ASSEMBLY 2 Sheets-Sheet 1 Filed Oct. 51,

F a (3 N H w m m m T vv QH m L w ww w L T v 1 A w m mm 0m av u m wm -IVW H C OW W Y WM m 1 wv 0% mm Q ww mm wwwn m S s w\ mm w9 w9 wm um mm ww on w mm a mm m mQ mg 09 om mw wm m on ov wl wm fiwf .m mm Qw mm em Q m\ *m 9 mm mm M June 13, 1967 H. L. LEVIN SECTIONALlZED TRAVELING WAVE TUBE ASSEMBLY 2 Sheets-Sheet 2 Filed Oct. 31 1962 ATTORNEY United States Patent 3,325,668 SECTIONALIZED TRAVELING WAVE TUBE ASSEMBLY Herbert L. Levin, Paterson, NJ, assignor to International Telephone and Telegraph Corporation, Nutle, N..l., a

corporation of Maryland Filed Oct. 31, 1962, Ser. No. 234,286 7 Ciaims. (Cl. 315-3.5)

This invention relates to traveling wave tubes and particularly to a novel arrangement therefor which permits several sections to be formed or replaced as independent units, thus providing a simplified, accurate, low cost construction.

The usual traveling wave tube is a complex combination of a plurality of components which require great care in manufacture and assembly. If it becomes necessary to replace a particular element, the procedure is quite difiicult, time consuming and costly. Often the entire tube must be scrapped. The tube generally comprises a unitary glass or metal evacuated envelope, a beam forming section including a stem providing electrical connections, an electron gun and support structure having a cathode, filament, grid and anode, input and output signal coaxial lines, a slow wave helix structure which provides signal interaction with the electron beam, a collector electrode and a magnetic field applying unit external to the tube envelope surrounding the helix. Each of these elements also include many smaller components which are generally assembled individually to form the complete device.

It is therefore the primary object of the instant invention to provide an improved construction for a traveling wave tube to be formed of a number of separate multi functional subassemblies which can readily be combined into a single compact unit by mass production techniques. The replacement of damaged or malfunctioning portions is thus simplified and each section may be inspected, tested, and stocked separately.

These results are accomplished by the formation of three main subassemblies or modules including a shellhelix portion, a gun assembly, and a stem assembly, each being formed as independent interchangeable units. The details of the invention will be more fully understood and other objects and advantages will become apparent in the following description and accompanying drawings, wherein:

FIGURE 1 shows a fragmentary sectional view of the entire tube assembly;

FIGURE 2 shows the stem portion;

FIGURE 3 shows the electron gun assembly;

FIGURE 4 shows the shell-helix section; and

FIGURE 5 is an end view of a portion of the shellhelix assembly.

As shown in FIGS. 1 and 2, the stem assembly portion includes a cup-shaped ceramic stem 12 having hollow metallic pins 14 and conductors 16 extending through the ceramic material to provide operating voltage connections from external leads 18 to the electron gun 20. A heliarc weld at the ends of pins 14 and conductors 16 provides an air-tight joint to which leads 18 are soldered. The ceramic stem 12 and another suitable insulator potting material 22, such as silicone rubber, provide isolation for high voltages on the leads and the shape of stem 12 reduces the effects on pulse shape due to the capacitance between pins 14 and the metallic tube shell or envelope 24. A metallic ring 26 is brazed to the ceramic stem 12 forming a subassembly which may then be heliarc welded to the inner end of tube envelope 24. The envelope comprises a gun shell portion having a flanged end 28 and an adjacent hole 30 into which an exhaust tubulation adapter 32 is crimped and brazed. The crimping eliminates the need for an additional brazing operation and provides a lip 3,325,661 Patented June 13, 196' for the braze fillet portion. After assembly and evacuatio of the entire tube, the adapter is sealed by a high pressur cold weld pinch-off. A cap 33 is crimped over the adapte to protect the seal. The adapter facilitates removal of th tribulation during salvage operations to permit reuse c the stem assembly. An added shield 34 is spot welded t and supported by one conductor having no external con nections. This provides protection against cathode deposi tion on the stem between conductors.

The electron gun 20, shown in FIGS. 1 and 3, include a cathode 35 and grid 36 positioned by a cylindrical cath ode support 38 and grid support ring 40. The cathode am the grid supports are brazed to wire supports 42 which an in turn brazed to three metallized ceramic rods 44, onl two being illustrated. The Wire supports also minimizr capacitance effects between elements and reduce heat los. from the cathode. The cathode is further supported by z sleeve 46 which also serves as a heat shield and focu: element. The sleeve extends into the cathode to act as 2 cylindrical reflector. Another cup-shaped heat shield 42 is spot welded at the cathode support and sleeve joint tc enclose heater 50. Insulated heater leads 52 are brough through the heat shield to a sheet metal connection plate 54 for later connection to the external leads.

The various gun elements are assembled as follows. The wires 42 are brazed to cathode support 38, grid support and rods 44, with the rod ends being brazed tc a gun mount plate 56, all in one operation. The cathode sleeve 46 is then inserted into the cathode support and spot welded. The heater and heat shield are added, the cathode is coated, and finally the grid is inserted into the grid support and spot welded to a retaining strip. Alternatively, in a simplified arrangement, the grid element may have a thin lip which is crimped over the edge of the grid support.

The gun mount plate or ring 56 to which the ends of ceramic rods 44 are brazed includes a stepped portion 58 at the outer edge. This step permits a lip 60 of gun support 62 to be crimped over to retain the gun assembly securely in position. This lip may easily be bent back to permit making replacements. The crimping also avoids the use of screws with attendant drilling and tapping operations, counterboring of holes to prevent flow of the brazed material into the threads and minimizes the likelihood of loosening under vibration.

The shell-helix assembly of FIGS. 1, 4, and 5 includes a cup-shaped gun flange structure 64 in which gun support 62 is brazed to the inner end. The outer edge of flange element 64 abuts flange 28 of gun envelope portion 24 forming a joint which is later heliarc welded. The joint provides access to the gun for assembly and replacement and facilitates the various crimping and brazing operations. A long tubular shell 66 is brazed to a central opening in the end of flange element 64. Gun support 62 is correspondingly in the form of an apertured disc and includes a radial slot 68, the edges of which form the outer conductor 70 of an input coaxial line 72, leading into tube 66. The slot simplifies the positioning and bending of inner conductor 74. An input adapter 76 fits into hole 78 through the edge of flange 64 and is stepped at the entrance 86 to slot 68. A further stepped portion 82 extends into and engages the edge 84 of the slot and the inner surface of flange 64 to complete outer conductor 70 and insure suflicient wall thickness for the unique joint. The elements forming outer conductor 70 are then brazed to the inner surface of support 62 and flange 64. The other brazing operations including that of tube 66 to supports 62 and flange 64 are accomplished at the same time. During assembly with the gun section care must be taken so that the holes for the rods in gun mount 56 are not located over the slot in gun support 62 to cause interruption of the input coaxial line. This may be facilitated by achining an indexing flat on gun mount 56. In a varia- )n of this design using an electron gun providing a nger beam convergence, the coaxial line may be brought it directly through the wall of tube 66 close to the end i the helix, rather than through the gun support and ange wall.

Abeam shaping anode 86 fits into the central aperture E flange 64 and support 62 and protrudes into tube 66. longitudinal slot 88 is provided in the anode to connue the path for outer conductor 70 from slot 68. Inner JIIdIIC'tOl 74 can then be bent at a right angle and conected to the slow wave helix structure 90. The ends of eramic rods 92 supporting the helix fit into a counterbore 4 in the anode which provides alignment for the helixhell assembly. The anode also serves to align the gun ssembly of which the gun mount 56 retains and engages 1e anode. The stepped hole 96 facing the gun provides a esired' cross-section for the electron beam which is pro- :cted into the helix along tube 66 under normal operatng conditions. The gun and anode provide a long throw :onverging beam having clearance for the input line and a roper relationship between the point of minimum beam nd the magnetic field of a periodic permanent magnetic tructure, not shown, abutting the outside of flange element 64 and mounted around tube 66 along the length of ielix 90. A very small diameter tubular envelope can hus be utilized.

A collector unit 98 contains the output coaxial line 100 0 which an output adapter 102 and coaxial seal 103 are- :onnected, a helix alignment counterbore 104 for the lelix and support rods, and a collector hole 106. The :nds of the rods and helix with attached output leads are nserted into the counterbore, the tube shell is slipped over he collector, the input lead is fed through the input idapter with insulator tubing fitted around the wire and :he anode is inserted. Thereafter, output adapter 102 and :oaxial seal 103 are brazed to collector 98 and an input :oaxial seal 107 is brazed to input adapter 76 to comalete the shell-helix assembly. Flange 28 of the envelope portion containing the stem and gun assemblies is then heliarc welded to the shell-helix flange portion to form a continuous tube enclosure.

It may thus be seen that the present novel traveling wave tube configuration provides a shell-helix assembly having both input and output coaxial lines and which is formed independently of the gun and stem assemblies. This permits testing of electrical characteristics such as voltage standing wave ratio match and insertion loss with out disturbing the coaxial lines in subsequent assembly operations and permits independent removal for repairs. The entire structure is aligned and assembled in a simple, accurate and compact manner.

While only a single embodiment has been illustrated, it is apparent that the invention is not limited to the exact form or use shown and that many other variations may be made in the particular design and configuration without departing from the scope of the invention as set forth in the appended claims.

What is claimed is:

1. A traveling wave tube comprising a first separable 6 unitary envelope portion, a stem assembly mounted there- 4- in, said stern assembly including an insulator body having conductors therethrough,

a second separable unitary envelope portion including therein an outer longitudinal tubular structure, a longitudinal slow wave helix and insulating support rods disposed within said tubular structure, input and output coaxial lines having connections at opposite ends of said helix, a collector at said output end of the helix having a central bore for projecting an electron beam therethrough and a tubular portion extending within said longitudinal tubular structure and around said helix and rods to align and support said helix and rods, an anode at said input end of the helix, and an electron gun support structure mounted adjacent said anode within said sec 0nd envelope portion and having a central aperture engaging said anode and longitudinal tubular structure, and

a third separable portion comprising an electron gun beam forming assembly having leads connected through said stem and detachable mounting means engaging said gun support structure and anode of said second envelope portion and being aligned by said anode, said first and second envelope portions having only one common joint forming a complete traveling wave tube enclosure.

2. The device of claim 1 wherein said common joint comprises peripheral flanges on each envelope portion.

3. The device of claim 1 wherein said input coaxial line passes radially through said second envelope portion and connects to a radial slot in said electron gun support, the edges of said slot forming the outer conductor of said coaxial line.

4. The device of claim 1 wherein said second envelope portion includes a cup-shaped flange section, said electron gun support being positioned at the inner end thereof.

5. The device of claim 4 wherein said anode includes a longitudinal slot completing said outer conductor connection to said helix.

6. The device of claim 4 wherein said electron gun detachable mounting means includes a plurality of insulator rods around said electron gun assembly and a plate engaging said electron gun insulatorrods and having a central apertured portion retaining said anode.

7. The device of claim 6 wherein said electron gun support has a deformable lip crimped around and securing said gun mounting plate. 7

References Cited UNITED STATES PATENTS 2,800,605 7/1957 Marchese 313-32 X 2,928,019 3/1960 Levin 3153.5 2,935,641 5/1960 Caldwell 31S3.5 2,939,995 6/1960 Danielson 315-3.5 2,958,800 11/1960 Wallace 315-35 X 3,007,076 10/1961 Anderson 315-3.5 3,227,913 6/1966. Disiman et al 3153.5

HERMAN KARL SAALBACH, Primary Examiner.

ARTHUR GAUSS, C. O. GARDNER, S. CHATMON,

Assistant Examiners. 

1. A TRAVELING WAVE TUBE COMPRISING A FIRST SEPARABLE UNITARY ENVELOPE PORTION, A STEM ASSEMBLY MOUNTED THEREIN, SAID STEM ASSEMBLY INCLUDING AN INSULATOR BODY HAVING CONDUCTORS THERETHROUGH, A SECOND SEPARABLE UNITARY ENVELOPE PORTION INCLUDING THEREIN AN OUTER LONGITUDINAL TUBULAR STRUCTURE, A LONGITUDINAL SLOW WAVE HELIX AND INSULATING SUPPORT RODS DISPOSED WITHIN SAID TUBULAR STRUCTURE, INPUT AND OUTPUT COAXIAL LINES HAVING CONNECTIONS AT OPPOSITE ENDS OF SAID HELIX, A COLLECTOR AT SAID OUTPUT END OF THE HELIX HAVING A CENTRAL BORE FOR PROJECTING AN ELECTRON BEAM THERETHROUGH AND A TUBULAR PORTION EXTENDING WITHIN SAID LONGITUDINAL TUBULAR STRUCTURE AND AROUND SAID HELIX AND RODS TO ALIGN AND SUPPORT SAID HELIX AND RODS, AN ANODE AT SAID INPUT END OF THE HELIX, AND AN ELECTON GUN SUPPORT STRUCTURE MOUNTED ADJACENT SAID ANODE WITHIN SAID SECOND ENVELOPE PORTION AND HAVING A CENTRAL APERTURE ENGAGING SAID ANODE AND LONGITUDINAL TUBULAR STRUCTURE, AND A THIRD SEPERABLE PORTION COMPRISING AN ELECTRON GUN BEAM FORMING ASSEMBLY HAVING LEADS CONNECTED THROUGH SAID STEM AND DETACHABLE MOUNTING MEANS ENGAGING SAID GUN SUPPORT STRUCTURE AND ANODE OF SAID SECOND ENVELOPE PORTION AND BEING ALIGNED BY SAID ANODE, SAID FIRST AND SECOND ENVELOPE PORTIONS HAVING ONLY ONE COMMON JOINT FORMING A COMPLETE TRAVELLING WAVE TUBE ENCLOSURE. 